1. Field of the Invention
The present invention relates to an audio/video recording apparatus and a method of multiplexing audio/video data, in particular, when recording audio/video data in a memory, such as a recording medium, together with supplementary data.
2. Description of the Related Art
In order to record supplementary data along with audio/video streaming data on a digital storage medium, it is known to multiplex the audio/video data with the additional information in a memory before then transferring the multiplexed data to the recording medium as a whole. This is illustrated schematically in FIG. 1 of the accompanying drawings. A single DMA process is used to transfer the multiplexed data from the memory to the recording medium so as to provide it as a whole to the recording medium. However, a number of individual DMA processes are required to transfer the sections of audio/video data and supplementary data to the intermediary memory.
Alternatively, the supplementary data can be recorded on the recording medium at a later time and at a different place to the main audio/video data. This is illustrated schematically in FIG. 2 of the accompanying drawings.
Both methods require system resources. In the case of multiplexing the data to an intermediary memory first, the system requires the system resources to do the multiplexing and the additional memory in which the multiplexed data is stored before transfer to the recording medium. On the other hand, when the supplementary data is stored at a different place on the storage medium to the audio/video data, the bandwidth to the storage medium is reduced, especially if the storage medium has a large seek time, for instance to move a mechanical read/write head to a new location.
This is particularly applicable to recording devices which record an input stream of audio/video data, together with supplementary data received with the audio/video data. A log of the supplementary data may be kept as the input audio/video data is received. It is possible to record the log after all of the audio/video data has been recorded on the recording medium. However, this makes reproduction undesirable, since, to reproduce the audio/video data together with the supplementary data, the reproduction device has to access different positions of the recording medium which are spaced widely apart. It is desirable, therefore, to interlace or multiplex the information from the log in with the audio/video data stored on the recording medium. As explained above, this was previously achieved by multiplexing the data in a separate memory before transfer to the recording medium.